Radio receiving system



July 18, 1933. F. P. ANDREWS 1,918,238

RADIO RECEIVING SYSTEM Filed Sept. 14, 1928 2 Sheets-Sheet l 10 /701? 1/76 216 71 000}; Receiver 6h 07? wove fiecezLzzerAQ L/Qe July 18, 1933. F P, ANDREWS 1,918,238

RADIO RECEIVING SYSTEM Filed Sept. 14, 1928 2 Sheets-Sheet 2 Hlllv v 6 a m g as YL fi f: Y: i

1 a it? Patented July 18,1933

UNITED STATES PATENT QFFICE RADIO RECEIVING SYSTEM Application filed September 14, 1928. Serial No. 306,016.

(GRANTED UNDER THE ACT OF MARCH 3, 1883, AS AMENDED APRZL 88, 1928; 370 0. G. 757) The invention described herein may be n'ianufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates in general to radio receiving systems and more particularly to improvements in remote electrically controlled variable condensers.

An object of this invention is to provide an electrically controlled variable condenser for the control of short wave receivers, by employing a movable condenser plate connectedto a voltmeter or ammeter mechanism, and a stationary condenser plate connected to the short wave receiver.

A further object is to provide an electrically controlled variable condenser for the control of a plurality of short wave receivers by employing stationary condenser plates connected separately to each short wave receiver, and a common movable condenser plate connected to a: voltmeter or ammeter mechanism.

A further object of my invention is to provide a remote control four channel receiving system involving the use of two electrically controlled variable condensers, each of which is adapted for the control of two short wave receivers.

With the foregoing and other objects in view, the invention consists in combination and arrangement of parts hereinafter set forth, certain embodiments of my invention beingillustrated in the accompanying drawings, in which:

Figure 1 is a diagrammatic view of the electrically controlled variable condenser controlling one short wave receiver;

Figure 2 is a diagrammatic view of the condenser arranged to control two short wave receivers;

.Figure 3 is a diagrammatic view of a tour channel receiving system-involving two remote electrically controlled variable condensers, each of which is adapted for the control of two short Wave receivers.

A movable condenser plate A of thin metal is connected to the pointer D grounded at g,

of a meter mechanism F, such as a voltmeter or ammetcr which is controlled from some distant point through lines G and H. A stationary plate B is insulated from the. plate A by means of an air of approximately ,4 inch, or a liquid dielectric may be used. This plate B is connected to the short wave receiver through the lead 13, and to the variable condenser C grounded at g. The electrostatic capacity of the condenser A B may be varied by adjusting the current flowing through the armature E. By connectin the condenser A B in parallel with one of the condensers C in the short wave receivers through the lead B; the adjustment of the receiver may be readily controlled over a limited frequency band.

In order to a; ply mydcvice for the control of a plurality oi. short wave receivers, I provide an electrically controlled variable condenser such as shown in Fi ure 2, in which the movable plate A of thin metal is attached to the point-er D. grounded at g, of a suitable voltmeter F with an armature E, the current iiow thrcuig'h which controlled at some distant point through lines G andH in the same manner described in connection with Fig ure 1.

ln this case with two short wave receivers No. 1 and No. 2, two stationary plates are employed, each being insulated from the movable plate A by an air gap of inch or other dielectric. The plate B is connected by lead B to the variable condenser C grounded at of the receiver No. 1 while plate K is connected through lead K to the variable condenser C grounded at of the receiver No. 2.

T he electrostatic capacity of condenser A B and of -i K is varied by adjusting the current flowing through the armature E. By connecting the condenser A B in parallel with the condenser in the receiver No. 1,"

V1 no adjustment of the receiver may be readily cont-rolled over a lir frequency band. In the same manner, the condenser A K being connected in parallel with condenser C of the receiver No. 2, the adjustment of this receiver may be readily controlled over a limited frequency band.

Referring more particularly to Figure 3-3, the four-channel receiver system shown there in employs two remote, electriCally-controlled variable condensers a and (1 the details of which are illustrated in Figure 2 and described in the specification referring to that figure.

Detectors Nos. 1, 2, 3 and 4 represent the radio frequency amplifier and detector circuits of four short-wave receivers. any one of which may be independently tuned for the signal desired. Each of these units will hereafter he referred to as receiver channels Nos. 1, 2, etc. The remote control variable condenser a is so connected that one of its fixed plates maybe associated with one of the frequency controlling condensers in receiver channel No. 1, and the other fixed plate asso ciated with one of the frequency controlling condensers in receiver channel No. 2, in such a manner that when the position of the mov able vane D (as shown in is varied, the frequency adjustment of either of the two receiver channels may be controlled. In a similar manner the remote control condenser (1 is associated with receiver channels Nos. 3 and 4.

All four of the receiver channels are connectcd in parallel with the input of the audio frequency amplifier No. l. The out-put of this audio frequency transformer is fed onto the cable No. 2.

Only one receiver channel may be used at one time. Selection of the desired channel is made by means of the circuit B R S X,, cable No. 1, relays r r r 1 and relays r r 7 and T in the following manner; current to the channel selecting circuit is supplied by battery B and the value of the current flowing through cable No. 1. and relays r r and r, is dependent upon the value of resistors R R and R These resistances are so adjusted that relays r r 1%,, and r. are permitted to function with varying amounts of current of the order indicated in Figure 3 M A for relay No. 1, M A for relay No. 2, M A for relay No. 3 and M A for relay No. 4)

A meter mechanism such as ammeter A functions to indicate the value of the current to the channel selecting circuit flowing through cable 1.

When the switch S at the control station is set on contact No. 4, a current of 30 milliamperes flows over cable No. 1, which actuates relay 1' closing the filament circuit of audio frequency amplifier No. 1. Since the relays 15,11 and 1' are adjusted for operation on greater than 30 M A, their armaturcs are not actuated; and, by means of a back contact on relay T the circuit is completed from 13 R X cable No. 2, X through the back contact of relay r filament control relay 1' and control condenser a to ground.

Thus when the circuit is completed in the manner described, frequency adjustment of receiver channel No. 1 may now be made by means of rheostat R and the. control condenser c The position of condenser a is indicated at the control. station by am meter A lVhcn the switch S at the control station is placed 011 contact No. 3, the selector relay 9 is actuated which opens the filament relay of receiver channel No. 1 and closes the filament, relay 1",; of the receiver channel No. 2 through the front contact of relay T and the back contact of relay 1' thus placing the receiver channel No. 2 in operation. The control condenser a, still remains in circuit receiving its control current through the relay m, etc. In the same manner, the receiver channels 3 or 4 may be selected by placing the switch S on contacts 2 or 1.

The signal output from the audio frequency amplifier No. 1 passes over the cable No. 2 through the condensers C. and (h and is prevented from being by-passed through the control mechanism by chokes X. and X The audio frequency amplifier No. 2 at the control station feeds directly into the opera tors telephone receivers or recording device.

Having thus described my invention what I claim is In combination with a plurality of radio receivers each having a variable condenser, a remote electrically controlled common means for controlling the variable condensers of each of the receivers, said means comprising a controlling variable condenser having stationary plates connected separately to the corresponding variable condenser of each receiver, and a common single movable plate connected to the pointer of the armature of a remotely controlled meter mechanism.

FRED P. ANDREWS.

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